Support frame for substrates

ABSTRACT

The present invention generally provides a system and method for supporting a substrate having a support frame that minimizes deflection encountered during thermal expansion in a processing chamber. In one embodiment, the support frame comprises one or more longitudinal members coupled to one or more transverse members. The transverse members preferably define a supporting surface on which a heated susceptor is mounted. The longitudinal member is preferably disposed below the heated susceptor, thus minimizing thermal expansion of the longitudinal member. Spacers made of thermally conductive material may be disposed at appropriate locations along the members to provide more uniform distribution of heat within the members.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a substrate processing system in theelectronics industry. More specifically, the invention relates to asystem and method for supporting substrates in a substrate processingsystem.

2. Background of the Related Art

Substrates on which physical vapor deposition (PVD), chemical vapordeposition (CVD), etching, electroplating, planarization and otherprocesses are performed are used to manufacture integrated circuits(ICs), flat panel displays (FPDs) and other electronic components. Roundsubstrates, typically known as wafers, are used to create a plurality ofICs by cutting the wafers into individual die after deposition and otherprocessing. The typical size for a semiconductor wafer is about 200 mmwith a thickness of less than 0.5 mm and a mass of about 60 grams.Typical substrate processing requires planar support of the substrate toensure uniform deposition across the substrate surface in the processingchamber. The relatively small size and light weight of the wafersrequire minimal structural support to retain a planar processingposition.

Conceptually, FPDs are produced by similar processes as are performed inthe fabrication of ICs, such as etching, deposition, and planarization.Generally, multiple metallic interconnects, liquid crystal cells andother devices are formed on a glass substrate to produce the FPD. Thevarious devices are integrated into a system that collectively is usedto create, for example, active matrix display screens in which displaystates are electrically created in individual pixels on the FPD. Overallprocessing uniformity across the entire surface of the FPD is criticalfor the FPD to function properly and defects in the FPD as a whole needto approach zero.

A typical glass substrate has increased in size from about 200 mm by 300mm to about 680 mm by about 880 mm and a mass of about 2 to about 3kilograms. The size is continuing to increase as the demand for largerscreens or displays increases.

FIG. 1 is a schematic cross-sectional view of a processing chamber 2,such as a CVD chamber having a top 4, bottom 6, sidewalls 8, a supportplate 18 and a susceptor 22 disposed therein to support an FPD substrate12. In general, CVD processing is the formation of a non-volatile solidlayer on a substrate by the reaction of vapor phase chemicals, termed"reactants", which contain the required constituents to be deposited.The reactants enter a system and are decomposed and/or reacted on asubstrate to form a desired layer of material thereon. Reactive gasesare flown through a gas inlet 14 into a gas manifold 16 that is mountednear the top of the chamber. An opening 10 is disposed in the sidewall 8to allow a robot (not shown) to deliver and retrieve the substrate 12 toand from the chamber. A support plate 18 is coupled to a support stem 20and supports the susceptor 22. The support plate 18 is typically made ofa single rectangular plate of ceramic material, such as aluminum oxide,and closely covers the area of the susceptor 22. The susceptor 22historically has been made of a single rectangular plate of aluminum andis typically heated with a heater (not shown) with energy supplied froma power source 24. A susceptor sized to accommodate the largersubstrates, such as a 680 mm by 880 mm substrate, can have a mass ofabout 130 kg. Even larger substrates may require a larger susceptor witha mass of about 230 kg.

Typical temperatures for CVD processes can reach up to about 430° C.Aluminum begins to exhibit "liquid" type properties at about 660° C.and, thus, at the operating ranges of the CVD processes, the aluminumsusceptor 22 can deflect and "droop" without adequate support. Theceramic material of the support plate 18 has been used to support theductile aluminum susceptor. However, ceramic is a relatively poorthermal conductor and, thus, demonstrates a temperature gradient betweena hotter upper surface of the support plate 18 that contacts the heatedsusceptor and a cooler lower surface of the support plate 18. Thethermal gradient can cause the hotter upper surface of the substrate toexpand a greater distance than the cooler lower surface, and as aresult, the support plate 18 deflects downwardly at its outer perimeter.Furthermore, as the support plate 18 deflects, the ductile aluminumsusceptor deflects in conformance with the deflected support plate. Asubstrate supported by the susceptor is prone to conform to thesusceptor and, thus, also deflects. As a result, the vertical spacingbetween the gas manifold 16 and the substrate 12 varies between acentral section of the substrate having a distance 34 from the manifoldand a peripheral region having a greater distance 36. The difference inspacing decreases deposition and other processing uniformity.

Therefore, there remains a need for a system having a support withreduced deflection for substrates, particularly larger substrates.

SUMMARY OF THE INVENTION

The present invention generally provides a system and method forsupporting a substrate having a support frame that minimizes deflectionencountered during thermal expansion in a processing chamber. In oneembodiment, the support frame comprises one or more longitudinal memberscoupled to one or more transverse members. The transverse memberspreferably define a supporting surface on which a heated susceptor ismounted. The longitudinal member is preferably disposed below the heatedsusceptor, thus minimizing thermal expansion of the longitudinal member.Spacers made of thermally conductive material may be disposed atappropriate locations along the members to provide more uniformdistribution of heat within the members and to compensate for verticaldeflection.

In another aspect, the invention provides a substrate processing system,comprising at least one chamber, a robot disposed in proximity to thechamber, and a support frame having at least one longitudinal member andat least one transverse member coupled to the longitudinal member. Inanother aspect, the invention provides a system for supporting asusceptor, comprising a longitudinal member supporting one or moretransverse members. In another aspect, the invention provides a systemfor supporting substrates with a support frame in a substrate processingsystem, the support frame comprising at least one longitudinal memberand at least one transverse member coupled to the longitudinal member.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features, advantages andobjects of the present invention are attained and can be understood indetail, a more particular description of the invention, brieflysummarized above, may be had by reference to the embodiments thereofwhich are illustrated in the appended drawings.

It is to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic cross-sectional view of a typical chemical vapordeposition (CVD) system having a unitary support plate.

FIG. 2 is a schematic cross-sectional view of a CVD chamber having asupport frame of the present invention.

FIG. 3 is a schematic side view of the support frame.

FIG. 4 is a schematic top view of the support frame.

FIG. 5 is a schematic side view of a spacer.

FIG. 6 is a schematic top view of the spacer.

FIG. 7 is a schematic of another embodiment of the spacer.

FIG. 8 is a schematic top view of a processing system used to advantagewith the support frame.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention generally provides a system and method forsupporting a substrate. The invention provides a support frame thatminimizes deflection encountered during thermal expansion and provides asurface on which a susceptor and/or substrate may be supported. Oneembodiment comprises one or more longitudinal members coupled to one ormore transverse members. Preferably, the transverse members are disposedin thermal communication with a susceptor. The longitudinal member isconnected to the transverse members at a location spaced from thesusceptor to avoid direct contact with the susceptor to minimizedifferential heating and resulting thermal expansion thereof.

FIG. 2 is a schematic side view of a chemical vapor deposition (CVD)chamber 38, such as a CVD chamber available from Applied KomatsuTechnology, Inc. having offices in Santa Clara, Calif. The chamber 38 isa parallel plate CVD chamber having a top 40, bottom 42, sidewalls 44and an opening 46 disposed in the sidewall through which substrates aredelivered and retrieved from the chamber. Chamber 38 contains a gasdistribution manifold 48, known as a diffuser, for dispersing processgases through perforated holes in the manifold to a substrate 50 thatrests on a susceptor 52.

Susceptor 52 is mounted on a support frame 54 and the support frame 54is mounted on a support stem 56. The susceptor 52 is typically a plateof aluminum and is heated by a resistive heater (not shown) embedded inthe susceptor 52. The heater provides rapid and uniform susceptor andsubstrate heating during deposition. The susceptor 52 and the substrate50 supported on the susceptor 52 can be controllably moved by a liftmotor 58, known as a Z-drive, to adjust the spacing between the manifold48 and the substrate 50. The spacing typically ranges between about 200mils to about 1000 mils. The susceptor 52 is movable between a lowerloading/off-loading position and an upper processing position that isclosely adjacent to the manifold 48. A lift plate 60 having lift pins 62is disposed below the support frame 54. When the support frame 54 islowered, the lift pins 62 protrude through spaces in the support frame54 and through holes 64 in the susceptor 52 to lift the substrate 50from the susceptor and facilitate delivery and retrieval of thesubstrate 50 to and from the chamber 38. Alternatively, holes can beprovided in one or more of the members of the support frame to allow thelift pins 62 to protrude through the members and through the susceptorto lift the substrate from the susceptor. An insulator 66 surrounds thesusceptor 52 and the substrate 50.

Deposition and carrier gases are input through gas supply lines 72 intoa mixing system 74 where they are combined and then sent to manifold 48.Alternatively, the mixing system 74 may be omitted and the gases flownto the manifold 48 directly. Generally, the process gas supply lines 72for each of the process gases include i) safety shut-off valves (notshown) that can be used to automatically or manually shut off the flowof process gas into the chamber, particularly when toxic gases are usedin the process, and ii) mass flow controllers (also not shown) thatmeasure the flow of gas through the gas supply lines. During processing,gases flown to manifold 48 are uniformly distributed across the surfaceof the substrate. The gases exhaust through a port 68 by a vacuum system70 having a throttle valve (not shown) to control the pressure in thechamber 38 by controlling the exhaust rate of gas from the chamber 38.

The deposition process performed in chamber 38 can be any process, suchas a thermal process or a plasma-enhanced process. In a plasma-enhancedprocess, a controlled plasma is formed adjacent to the substrate by RFenergy applied to gas distribution manifold 48, or another plasmaenergizing device or structure, from an RF power supply 76. Thesusceptor 52 is grounded and the manifold 48 is electrically isolatedfrom the chamber surfaces. The plasma creates a reaction zone betweenthe gas distributor manifold 48 and the substrate 50 that enhances thereaction between the process gases. RF power supply 76 can provideeither single or mixed frequency RF power to manifold 48 to enhance thedecomposition of reactive species introduced into chamber 38. A mixedfrequency RF power supply typically provides power at a high RFfrequency (RF1) of about 13.56 MHz and at a low RF frequency (RF2) ofabout 350 kHz.

Typically, any or all of the chamber linings, gas distribution manifold48, support stem 56, and various other chamber hardware are made ofmaterial such as aluminum or aluminum oxide. An example of such a CVDchamber is described in U.S. Pat. No. 5,000,113, entitled "ThermalCVD/PECVD Chamber and Use for Thermal Chemical Vapor Deposition ofSilicon Dioxide and In-situ Multi-step Planarized Process," issued toWang et al., and assigned to Applied Materials, Inc., the assignee ofthe present invention.

The lift motor 58, the gas mixing system 74, and the RF power supply 76are controlled by a system controller 78 over control lines 80. Thechamber includes analog assemblies such as mass flow controllers (MFCs),RF generators, and lamp magnet drivers that are controlled by the systemcontroller 78 which executes system control software stored in a memory82. Motors and optical sensors are used to move and determine theposition of movable mechanical assemblies such as the throttle valve ofthe vacuum system 70 and lift motor 58 for positioning the susceptor 52.The system controller 78 controls all of the activities of the CVDchamber and preferably includes a hard disk drive, a floppy disk drive,and a card rack. The card rack contains a single board computer (SBC),analog and digital input/output boards, interface boards and steppermotor controller boards. The system controller preferably conforms tothe Versa Modular Europeans (VWE) standard that defines board, cardcage, and connector dimensions and types.

FIG. 3 is a schematic side view of the support frame 54. A support stem56 is coupled to the support frame 54 and the support frame 54 supportsthe susceptor 52. In one embodiment, the support frame 54 comprises atleast one longitudinal member 84 and at least one transverse member 86,preferably a plurality of transverse members, mounted on thelongitudinal member 84. Alternatively, the longitudinal member and thetransverse members could be disposed in a single plane, for example, byslotting each member to fit the corresponding other member. Thelongitudinal member 84 and transverse members 86 have rectangularcross-sections, although other shapes can be used. Preferably, thesupport frame interposes the transverse members between the heat source,such as a heated susceptor, and the longitudinal member, so that thelongitudinal member does not directly contact the heated susceptor toreduce thermal expansion of the longitudinal member. The longitudinaland transverse members are made of a ceramic material such as aluminumoxide or other structurally suitable material. In some instances, thematerial can be metal alloys that are heat resistant and have a lowercoefficient of expansion compared to aluminum, such as stainless steel.

FIG. 4 is a schematic top view of the support frame shown in FIG. 3. Aplurality of transverse members 86a-d are positioned above alongitudinal member 84. The transverse members are spaced apart fromeach other to define lateral spaces 88a-c. Preferably, the thermalexpansion of the longitudinal member is reduced by avoiding directcontact with the heated susceptor 52 (shown in FIG. 3).

It is believed that the support frame 54 dissipates thermal expansionamong several smaller members. The members of the present invention aremore able to uniformly expand and, thus, stress cracks are reduced. Forinstance, the greatest expansion of the longitudinal member occurs inthe direction 90 along the length of the longitudinal member. Theexpansion of the longitudinal member 84 in the direction 90 has lesseffect on the transverse members 86a and 86b compared to a typicalsupport plate because of the separation between the transverse members.The expansion is divided among the transverse members, preferablyseparated by lateral spaces 88a-c, so that stresses on the material arereduced. Likewise, the total expansion of the transverse member 86 inthe direction 92 in contact with a uniformly heated susceptor wouldgenerally be greater at the transverse member ends than at the centerbecause of the cumulative effect of the length of the transversemembers. Therefore, the expansion of the transverse members in thedirection 92 would have less transverse effect on the centrally locatedlongitudinal member coupled to the transverse member compared to atypical support plate.

The support frame constructively uses the low, compared to aluminum,heat transfer coefficient to thermally insulate the longitudinal memberfrom the susceptor heat and further reduce thermal expansion.Preferably, only the transverse members 86 contact the susceptor 52shown in FIG. 3. The thermal resistance of the ceramic material in thetransverse members 86 reduces or eliminates the heat conducted to thelongitudinal member 84. It is believed that thermal expansion of thelongitudinal member is minimized at least along the length of thelongitudinal member because the longitudinal member is not in thermalcontact with the heated susceptor by being mounted away from thesusceptor. As a result, the longitudinal member has less of a thermalgradient from the top surface to the bottom surface and deflection atleast in the longitudinal direction is minimized.

The support frame 54 can also include spacers 94, shown assembled on thesupport frame 54 in FIGS. 3 and 4. The spacers 94 accommodate thedeflection of the support frame, if any deflection occurs. For instance,the transverse members 86 may deflect by being in contact with a heatedsusceptor 52. One or more spacers can be assembled to the support framepreferably along any top surface of the transverse members 86 wheredeflection occurs, which may be experimentally determined, to provide aplanar alignment of the upper surface of spacer(s) and upper surfaces ofthe support frame to maintain planarity of the susceptor 52. Forexample, a spacer 94 may be disposed on one end of one transverse member86a and on another end of another transverse member 86d if deflection isdetermined to occur at those locations. Alternatively, each end of eachmember may have spacers disposed thereon.

The spacers 94 are generally placed in position prior to any deflection.The spacers would support the susceptor 52 above at least a portion ofthe surface of the support frame 54. When the support frame 54 deflectsin processing, the susceptor 52 could be supported by the spacer(s) anda portion of the support frame, generally the center of the supportframe, to establish the susceptor in a satisfactory planar position.

FIG. 5 is a schematic side view of the spacer 94. FIG. 6 is a schematicbottom view of the spacer. The spacer 94 is "C" shaped and includes twoends 96. As best viewed in FIG. 6, the spacer is rectangular in shape.Preferably, the spacer ends 96 are angled and sized to clasp thetransverse members 86 and remain in position until removed.

The spacers are preferably made of conductive material, such asaluminum. The conductive material allows heat to be conducted moreuniformly throughout the spacer and around the edges 96 to the sides ofthe transverse members 86. Thus, the heat on the upper surface of thetransverse members is allowed to thermally diffuse to the lower surfacesof the transverse members. The thermal gradient in the transversemembers is reduced in the region of the spacer(s) and stress cracking ofthe members is further reduced.

FIG. 7 is a schematic of another embodiment of a spacer 98. The spacer98 can form a band around, for example, a transverse member 86. Thespacer 98 can include a bottom 99 so that spacer 98 forms a "boot". Itis believed the spacer 98 distributes heat more evenly around the memberthat the spacer surrounds.

The CVD chamber shown in FIG. 2 can be incorporated into a system usingother chambers as well. For instance, FIG. 8 is a schematic top view ofan exemplary cluster processing system 100. A portion of the lid 124 hasbeen cut away to reveal details of the processing system 100. Theprocessing system 100 is typically known as a cluster tool. One suchsystem is available from Applied Komatsu Technology, Inc. The details ofan exemplary staged-vacuum substrate processing system is disclosed inU.S. Pat. No. 5,186,718, entitled "Staged-Vacuum Wafer Processing Systemand Method," Tepman et al., issued on Feb. 16, 1993, which isincorporated herein by reference. The exact arrangement and combinationof the chambers may be altered for purposes of performing specific stepsof a fabrication process. Other processing systems, such as inlineprocessing systems, could be used instead of the cluster tool processingsystem.

The processing system 100 generally comprises a plurality of chambersand robots and is preferably equipped with a microprocessor/controller102 programmed to control the various processing methods performed inthe processing system 100. A front-end environment 104 is shownpositioned in selective communication with a pair of load lock chambers106. A pod loader 108 disposed in the front-end environment 104 iscapable of linear and rotational movement to shuttle cassettes ofsubstrates to and from the load locks 106. The load locks 106 provide afirst vacuum interface between the front-end environment 104 and atransfer chamber 110. A robot 112 is centrally disposed in the transferchamber 110 to transfer substrates from the load locks 106 to one of thevarious processing chambers 114 and service chambers 115. The robot 112is a frog-leg type robot capable of extension, retraction, and rotationand is actuated by a stepper motor. A support member 116 connected tothe robot linkage 118 is adapted to support a substrate 120 duringtransfer through the transfer chamber 110 and between the chambers 114,115 and the load locks 106. The processing chambers 114 may perform anynumber of processes such as PVD, CVD, electroplating and etching whilethe service chambers 115 are adapted for degassing, orientation, cooldown and the like. A number of view ports 122 formed in a lid 124 of thetransfer chamber 110 provide visual access into the transfer chamber110. While the above system is exemplary, the invention has applicationin any arrangement that supports a substrate, and, thus, it isunderstood that other applications of the invention are contemplated.

Variations in the orientation of the support frame, support members,substrates, chambers, and other system components are possible.Additionally, all movements and positions, such as "above", "top","below", "under", "bottom", "side", described herein are relative topositions of objects such as the support frame, support members,substrates, and chambers. Accordingly, it is contemplated by the presentinvention to orient any or all of the components to achieve the desiredsupport of substrates in a processing system.

While foregoing is directed to the preferred embodiment of the presentinvention, other and further embodiments of the invention may be devisedwithout departing from the basic scope thereof and the scope thereof isdetermined by the claims that follow.

What is claimed is:
 1. A substrate processing system, comprising:a) atleast one chamber; b) a robot disposed in proximity to the chamber; andc) a support frame for supporting a susceptor having at least onelongitudinal member and a plurality of transverse members coupled to thelongitudinal member, the transverse members arranged to define at leastone lateral space therebetween.
 2. The system of claim 1, wherein the atleast one longitudinal member supports least two of the transversemembers.
 3. The system of claim 1, further comprising a support stemcoupled to the support frame.
 4. The system of claim 1, furthercomprising a susceptor disposed between the support frame and asubstrate supporting surface on the susceptor.
 5. The system of claim 1,wherein the transverse members are mounted on the longitudinal memberand defines a susceptor supporting surface on an upper surface thereof.6. The system of claim 5, wherein the transverse members are disposedbetween a susceptor and the longitudinal member.
 7. The system of claim6, wherein the transverse members contact the susceptor and insulatesthe longitudinal member from the susceptor.
 8. The system of claim 1,further comprising at least one spacer coupled to the support frame. 9.The system of claim 1, wherein at least a portion of the support framecomprises ceramic material.
 10. The system of claim 7, wherein thetransverse members comprise a ceramic material.
 11. An apparatus forsupporting a susceptor in a substrate processing system, comprising asupport frame having at least one longitudinal member supporting aplurality of transverse members, the transverse members arranged todefine at least one space therebetween.
 12. The apparatus of claim 11,wherein the at least one longitudinal member is coupled to the pluralityof transverse members and provides support for the transverse members.13. The apparatus of claim 12, wherein the transverse members aremounted on the longitudinal member and define a susceptor supportingsurface on an upper surface thereof.
 14. The apparatus of claim 11,further comprising a support stem coupled to the support frame.
 15. Theapparatus of claim 12, wherein at least two of the transverse membersare disposed along a length of the at least one longitudinal member in aspaced relationship to one another.
 16. The apparatus of claim 12,wherein the support frame is disposed in a substrate processing systemand the transverse members are disposed between a susceptor in theprocessing system and the longitudinal member.
 17. The apparatus ofclaim 16, wherein the transverse members contact the susceptor andinsulate the longitudinal member from the susceptor.
 18. The apparatusof claim 11, further comprising at least one spacer coupled to thesupport frame.
 19. The apparatus of claim 11, wherein at least a portionof the support frame comprises ceramic material.
 20. The apparatus ofclaim 17, wherein at least one of the transverse members comprises aceramic material.
 21. A system for supporting a susceptor with a supportframe in a substrate processing system, the support frame comprising:a)at least one longitudinal member; and b) a plurality of transversemembers coupled to the longitudinal member, at least a portion of thetransverse members being disposed between the susceptor and thelongitudinal member.
 22. The system of claim 21, further comprising atleast one spacer coupled to at least one of the transverse members thatengages a substrate supported on the transverse members.